\[\boxed{\mathbf{199.}}\]
\[240 + 3 = 243\]
\[240 + 30 = 270\]
\[240 + 300 = 540\]
\[420 + 500 = 920\]
\[420 + 50 = 470\]
\[420 + 5 = 425\]
\[310 + 40 = 350\]
\[310 + 4 = 314\]
\[310 + 400 = 710\]
\[530 + 2 = 532\]
\[530 + 200 = 730\]
\[530 + 20 = 550\]